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Lenovo G510 - LA9641P No Voltage TL_INVT_PWM After 3V Inverter Replacement & Matrix Backlight Issue

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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
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  • #1 17022006
    nuda
    Level 18  
    Hello, the plate after replacing the 3V inverter (it was damaged) is the lack of matrix backlight. The rest of the voltages in the LCD connector are correct, after TL_INVT_PWM. With the tape connected, the voltage at pin 8 (TL_INVT_PWM) jumps to a fraction of seconds to 1v followed by 0V. No tape connected all the time 4.18V. The UT2 change did not give me any suggestions. Bios done without improvement. After supplying voltage on TL_INVT_PWM, the backlight appears.
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  • #2 17022052
    sylweksylwina
    Moderator of Computers service  
    Are the transitions from KBC and UT2 to resistors R441 and R431?
  • #3 17022059
    nuda
    Level 18  
    I can not locate them because there are no markings for the resistors on the disc. I forgot to write that on the KBC leg 25 (EC_INVT_PWM) voltage 3.3V
  • #4 17022431
    sylweksylwina
    Moderator of Computers service  
    It's probably lost somewhere along the way. Resistors are somewhere around the LVDS connector.
  • #5 17023982
    nuda
    Level 18  
    Nowhere are these resistors visible, not even on a different disc as I have on parts. It would be useful for the LA-9641P boardview.
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  • #6 17024320
    sylweksylwina
    Moderator of Computers service  
    Search between UT2 and LVDS and KBC connector and connector.
    Set the multimeter on the diode test, apply one probe to the connector and fly all resistors :) If you do not find it will be somewhere damaged path start from the other side, KBC and UT2. Somewhere they must be :) Visually, you can not track down the tracks because you can go in the middle of the disc.
  • #7 17024472
    nuda
    Level 18  
    This is how I made the transition between UT2 and LVDS (though the resistor is missing), not that I can find a resistor between the NCB and the LVDS, no transition to the connector.

    Edit. Do not quote the preceding posts in their entirety. RADU23
  • #8 17024515
    Stani12
    Level 28  
    I have boardview only I can not open it any program. It has a .brd extension but nothing moves it. Removed from vinafix.
    I do not have time to search. Write how to attach it to the post I throw it. It has 11.1Mb.

    Edit.
    I have already opened the allegro program and I will put a screenshot right away.
  • #9 17024528
    nuda
    Level 18  
    Stani12 wrote:
    I have boardview but I can not open it with any program. It has a .brd extension but nothing moves it. Removed from vinafix.
    I do not have time to search. Write how to attach it to the post I throw it. It has 11.1Mb.


    It would help me a lot and I would look for a program to move it, it's best to add it to the Computer Instr. Service.
    Or just add an attachment in this topic
  • #10 17024615
    Stani12
    Level 28  
    At the beginning p Lenovo G510 - LA9641P No Voltage TL_INVT_PWM After 3V Inverter Replacement & Matrix Backlight Issue I am asking for info or such a disc shape.
    I found the R441 resistor. R431 no. I did not watch the diagram so I do not know if it is represented.
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  • #11 17024622
    nuda
    Level 18  
    Yes the disc is the same
  • #12 17024663
    Stani12
    Level 28  
    Lenovo G510 - LA9641P No Voltage TL_INVT_PWM After 3V Inverter Replacement & Matrix Backlight Issue The arrow indicates R441. Lenovo G510 - LA9641P No Voltage TL_INVT_PWM After 3V Inverter Replacement & Matrix Backlight Issue

    Added after 37 [minutes]:

     You do not answer anything so I do not know if you already have everything or something missing.
  • #13 17024974
    nuda
    Level 18  
    PR401 is not manned on these discs, I have a second part and I also do not have that reistor. I do not have the KBC EC_INVT_PWM connection to TL_INVT_PWM as it is in the schematic. So it comes out that the UT2 system is responsible for TL_INVT_PWM only that after connecting the matrix the voltage disappears.
  • #14 17025474
    Stani12
    Level 28  
    The voltage was measured on both sides of the resistor? Maybe a defective resistor ?. Also check if there is a short to ground in the ribbon (TL_INVT_PWM line).
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  • #15 17031702
    nuda
    Level 18  
    Forgive me that only now is writing back but I gave up on the weekend.
    So, there is no resistor PR441. The voltage on the leg 8 LVDS without a plugged matrix is 3.6V, after connecting it jumps to 2.5V for a fraction of a second and then drops to zero. I also checked beforehand whether there is a short circuit on the TL_INVT_PWM line and there is no short circuit, with a 124k ohms connected without 128k ohms. I slowly think that the new UT2 chip is damaged, but I'm not sure.
  • #16 17032331
    Stani12
    Level 28  
    There is no resistor but is the path ?.
    I can reprogram the BIOS and kbc.
    Maybe a different wire is shorted and the system turns off the backlight.
  • #17 17033459
    nuda
    Level 18  
    The paths are connected in spite of the lack of a resistor (on both boards in the same way), the bios I uploaded normally from the manufacturer did not improve the problem.
    The tape or layout will be replaced by the tape later. Because I'm left with nothing else.
  • #18 17033864
    Stani12
    Level 28  
    After all, the tape can be measured for shorts and gaps. Enter the matrix model.
  • #19 17050744
    nuda
    Level 18  
    I come back after a long break, I could not afford to sit at this record for so much time. So the UT2 replacement (two times) did not work, the matrix tape and other efficient components. I left this record for a while. The client could not wait any longer, so he decided to buy a new disc (old bought for further repair / diagnosis). Subject to be closed.
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Topic summary

✨ The discussion revolves around a Lenovo G510 laptop experiencing a matrix backlight issue after replacing a damaged 3V inverter on the LA-9641P motherboard. The user reports that the TL_INVT_PWM signal shows a brief voltage spike to 1V before dropping to 0V when the LCD is connected, while it remains at 4.18V without the connection. Various users suggest checking the resistors R441 and R431, which are difficult to locate due to lack of markings. The user confirms that the resistors are not visible and discusses the possibility of a damaged path or a defective UT2 chip. Despite attempts to reprogram the BIOS and check for shorts, the issue persists, leading the user to consider replacing the matrix tape. Ultimately, the user decides to close the topic as the client opted to purchase a new laptop.
Generated by the language model.

FAQ

TL;DR: 4.18 V on TL_INVT_PWM with panel unplugged; "After supplying voltage on TL_INVT_PWM, the backlight appears." That points to a control-path fault around UT2/R441/LVDS on Lenovo G510 LA‑9641P. [Elektroda, nuda, post #17022006]

Why it matters: It helps techs and G510 owners fix no‑backlight issues faster by checking the right signal path.

Quick Facts

What is TL_INVT_PWM on the LA-9641P and what does it control?

It is the backlight control/PWM line to the panel inverter circuitry. When you manually drive TL_INVT_PWM high, the backlight turns on. If connecting the panel pulls it low, the control path is collapsing under load. That points to cabling, connector, or the signal conditioning stage. "After supplying voltage on TL_INVT_PWM, the backlight appears." [Elektroda, nuda, post #17022006]

Which LVDS pin carries TL_INVT_PWM on the Lenovo G510?

Pin 8 of the LVDS connector carries TL_INVT_PWM. Users measured a brief ~1 V pulse at pin 8 when the panel connects, followed by a drop to 0 V. With the panel disconnected, they saw a steady high level at that pin. [Elektroda, nuda, post #17022006]

Where is resistor R441 on the LA-9641P board?

R441 is located near the LVDS connector area. Use a high‑resolution board photo or a boardview to identify it, then probe both sides for voltage and continuity. A shared screenshot marks R441’s position with an arrow for guidance. [Elektroda, Stani12, post #17024663]

My PR441 footprint is empty. Is that normal, and does the path still connect?

Yes. Some LA‑9641P boards ship with PR441 unpopulated. Technicians confirmed the TL_INVT_PWM path remains connected across the pads despite the missing part. Verify continuity across the footprint to be sure on your revision. [Elektroda, nuda, post #17033459]

How can I trace TL_INVT_PWM from KBC to LVDS without a boardview?

Use the diode‑test mode on a multimeter to follow the net across nearby resistors. An expert tip: "Search between UT2 and LVDS." Tracks can run on inner layers, so probe from the LVDS pin to surrounding passives, then toward KBC and UT2. [Elektroda, sylweksylwina, post #17024320]

What should I see on KBC pin 25 (EC_INVT_PWM)?

Expect about 3.3 V at KBC pin 25 if the EC is asserting the backlight control. If that node is healthy while TL_INVT_PWM collapses at the LVDS, the fault lies between EC/KBC output and the LVDS pin. [Elektroda, nuda, post #17022059]

Why does TL_INVT_PWM read high unplugged but drop when the panel connects?

Unplugged, the line sits high because no load pulls it down. When the panel connects, the path likely sinks the line, disabling backlight. Users observed a brief ~1 V pulse then a drop to 0 V on connect. [Elektroda, nuda, post #17022006]

How do I check the LVDS ribbon for a TL_INVT_PWM short or load?

Measure resistance from TL_INVT_PWM to ground with and without the ribbon connected. Reported readings of roughly 124–128 kΩ indicate no hard short. A much lower value suggests a loading fault in the cable or panel circuitry. [Elektroda, nuda, post #17031702]

Will reflashing BIOS or EC/KBC fix the no‑backlight condition?

A BIOS reflash did not restore TL_INVT_PWM in this case. Before reflashing the EC/KBC, confirm EC_INVT_PWM is present and trace continuity toward the LVDS. Firmware changes rarely fix a pulled‑low PWM line. [Elektroda, nuda, post #17022006]

Should I replace UT2 to restore the PWM signal?

Treat UT2 replacement as a last resort. One technician replaced UT2 twice and the PWM dropout persisted, forcing a board replacement. "UT2 replacement (two times) did not work." Validate the path and cable first. [Elektroda, nuda, post #17050744]

How do I open an LA-9641P .brd boardview file?

A user opened the .brd boardview using an Allegro program and shared screenshots. Install Cadence Allegro Free Viewer or a compatible viewer to inspect nets like TL_INVT_PWM and locate R441 quickly. [Elektroda, Stani12, post #17024515]

Could the LVDS cable or the panel be causing the PWM to collapse?

Yes. Measure the ribbon for shorts and open lines before swapping boards. If measurements are inconclusive, try a known‑good cable or panel to isolate the load that pulls TL_INVT_PWM low. Provide the panel model when seeking help. [Elektroda, Stani12, post #17033864]

Is forcing TL_INVT_PWM high a valid test?

Yes, as a quick diagnostic. Manually driving TL_INVT_PWM high made the backlight appear, proving the backlight power chain worked. Do not leave it forced; fix the control path instead. [Elektroda, nuda, post #17022006]

I cannot find R431/PR401 on my board. Is that expected?

It can be. Some resistors are unmarked or unpopulated on certain LA‑9641P revisions. One user noted PR401 was not populated, and TL_INVT_PWM routing differed from the schematic expectation. [Elektroda, nuda, post #17024974]

What’s a concise workflow to diagnose TL_INVT_PWM loss on G510?

  1. Check EC_INVT_PWM at KBC pin 25 for ~3.3 V.
  2. Trace TL_INVT_PWM from LVDS pin 8 through R441/PR441 using diode‑test.
  3. Measure TL_INVT_PWM‑to‑GND resistance; swap cable or panel if it loads the line. [Elektroda, sylweksylwina, post #17024320]
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